Critical parameters of an injection procedure are determined by a number of variables, including, for example, syringe diameter, syringe length, syringe material and fluid composition/concentration. Among the affected injection procedure parameters are fluid volume delivered, flow rate, fluid pressure, and limits of injector piston travel. In current injector systems, syringe size is generally determined either (1) manually by action of an operator who enters the syringe size or type into the injector software, or (2) automatically by means of switches on the injector head which are mechanically coupled to raised or sunken elements on the syringe. See, for example, U.S. Pat. Nos. 5,741,232, 6,090,064 and 5,873,861, assigned to the assignee of the present application, the disclosures of which are incorporated herein by reference. FIG. 1A illustrate sunken elements or detents 2 and 2′ positioned around the arc of flanges 3 and 3′ in a rear, engagement flange portion of a syringe 4 as described in U.S. Pat. No. 5,873,861. Syringes 4, including detents 2 and 2′, have been fabricated from, for example, clear or opaque, polymeric materials. Detents 2 and/or 2′ cooperate with one or more correspondingly positioned switches 6 in a powered injector 8 illustrated in FIG. 1B. The presence or absence of one or more of detents provides a code that represents syringe configuration.
Constraints of mechanical and electrical design, however, limit the number of such automatic detection switches. Indeed, only limited syringe configurations are automatically detected with present systems. Additionally, failure of moving mechanisms is also a problem. Moreover, certain electrical and mechanical encoding systems can significantly increase manufacturing costs of a syringe and/or injector. Other currently available methods of encoding and sensing syringe configuration include the placement of bar codes and corresponding sensors upon the syringe and injector, respectively, as disclosed in U.S. Pat. No. 5,997,502. Bar code systems, however, suffer from some of the same problems as the electromechanical systems discussed above.
As used herein, the term “syringe configuration” is used to encompass all information about a particular syringe, including, but not limited to, information about the mechanical properties of a syringe (for example, material, length and diameter) as well as information about the contents of the syringe (for example, volume and composition). With the advent of new syringes, and especially prefilled syringes, the need to accurately encode and sense (or read) syringe configuration variables is heightened. The information on syringe configuration can be used by a powered injector to control the injection procedure as a function of defined syringe configuration/injection parameters. Moreover, a record of data associated with an injection procedure may be kept, for example, to satisfy accurate billing and cost information requirements under managed health care. A record may be maintained of information such as the type of syringe used, the amount of contrast medium used, the type of contrast medium used, the sterilization date, the expiration date, lot codes, the properties of the contrast media, and/or other clinically relevant information. Such information can be recorded digitally for sharing with computerized hospital billing systems, inventory systems, control systems etc.
It is very desirable for a syringe-based injector system to automatically determine such information. It is, therefore, an object of this invention to provide encoding of information to be shared between a syringe and a powered injector for use therewith.